Fertilizers are responsible for over half of global food production, but there are areas in world with nutrient deficiency and other areas of nutrient excess.
Managing mineral plant nutrients requires careful application of science and skill to meet production, environmental, and social goals.

Thursday, June 12, 2014

Nutrient Deficiency Symptoms... Don't wait until you see them

Plant
nutrient deficiency symptoms begin to appear when one of the essential
nutrients is lacking.

Iron-deficient cowpeas

Some­times deficiencies appear early in the growing season when soils
are cold or wet, and when root activity is low. Deficien­cies are also commonly
observed later in the season when the soil cannot satisfy the high nutrient
demand of a rapidly growing crop. Whether the deficiency is caused by poor root
uptake or low nutrient-supplying power of the soil, proper management practices
can help alleviate these problems.

Deficient
plants do not initially show any obvious symptoms of nutrient shortage other
than slower growth, which can also be due to many factors. In the case of a mild deficiency,
plants may never show a visual symptom ex­cept slow growth and reduced yield.

Nutrient
deficiency causes a disruption in any number of essential metabolic processes
within the plant. Crops
mature unevenly because deficiencies rarely occur uniformly across entire
fields. This leads to lower yield, harvest­ing difficulties and poorer crop
quality. And as previously stated, this can all occur without diagnostic
symptoms appearing.

Potassium-deficient cucumber

When
deficiency symptoms become noticeable, severe stress is already occurring and
steps should be considered to overcome the problem, if it is practical and
economical to do. The
effects of other stresses such as drought and pests can complicate diagnoses.
Another problem is that not all deficiencies produce clear-cut symptoms. Then
there is the possibility of multiple deficiencies. The most severe deficiency
may be manifested first. Knowing which nutrients are mobile or immobile within
the plant is helpful in pinpointing the cause of the deficiency symptom.
Diagnosing symptoms also requires understanding of specific crop colors and
markers. It is worth noting that some crops are more susceptible to visible
symptoms than others.

Plant
analysis (tissue testing) is useful for diagnosing specific nutrient
deficiencies as they arise. It is best when nutrient concentrations in deficient
plants growing in problem areas are compared with healthy plants to identify
the differences. It is also helpful to collect soil samples for analysis from
the two areas at the time the plant samples are col­lected.

Zinc-deficient potato

Tissue testing
also is valuable for monitoring plant health during the season to verify that
nutrient concentrations do not drop below nor exceed established critical
values. Guidelines have been developed for many crops for what the ap­propriate
nutrient concentrations should be during various growth stages. Supplemental
fertilization should be considered if the concentrations fall below these
established thresholds.

Pre-season
soil testing should also be part of a strategy for preventing nutrient
shortages. In addition to helping avoid plant stress, soil analysis will allow
decisions to be made that will avoid over or under application of fertilizer
and resulting economic inefficiency.

The
International Plant Nutrition Institute (IPNI) has a large database of nutrient
deficiency images that is continually growing. Visit the website at:
http://media.ipni.net. Additionally, a collection of over 500 of our best plant
nutrient deficiency photos is available for purchase at
http://ipni.info/nutrientimagecollection. A condensed version of this
collection is available as an app for iPhones and iPads at
http://www.ipni.net/article/IPNI-3273. When nutrient deficiency symptoms
appear, first act quickly to diagnose the problem and then make plans to
correct it and to avoid having them reoccur in the future.

Potassium-deficient cotton

This blog posting originally appeared as part of the Plant Nutrition Institute quarterly newsletters "Plant Nutrition Today". The entire series can be viewed here.

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About Me

I am a soil scientist with interest in managing plant nutrients in the best way possible. I am fortunate to be able to work in research and education to be able to accomplish this goal.
After receiving a PhD in Soil Science at the University of California (Riverside), I worked as a Research Scientist for the U.S. government, as a Professor of Soil Science, and now I work for a not-for-profit institution. It's been a wonderful experience!